The present invention relates to a divalent silver oxide cell, and more particularly to a divalent silver oxide cell with a remarkably improved electrical characteristic, storing characteristic and leakage resistant characteristic by improvement of its stability in the alkaline solution and of the manufacturing method of its positive electrode.
A conventional divalent silver oxide cell, without a stabilizer lacks stability since O.sub.2 gassing volume caused by dissolution aqueous alkaline solution is large. Thus the conventional divalent silver oxide is disadvantageous in that it dissolves by itself in aqueous alkaline solution to reduce the electrical capacity as the divalent silver oxide. Further the O.sub.2 gas evolved by dissolution of the divalent silver oxide oxidizes a separator so as to deteriorate it or to promote the self-discharge of the cell. The O.sub.2 gas at the positive electrode diffuses and penetrates into the negative electrode through the separator to oxidize zinc and deteriorates the electrical capacity thereof. The acceleration of oxidation of zinc causes the zinc surface to be coated with a passive coating layer such as zinc oxide and stops the discharge of the cell even if active zinc remains as the active material of the cell.
Thus the cell using the conventional unstable divalent silver oxide at the positive electrode without adding the stabilizer is inferior with respect to the storing characteristic.
The cell using the conventional divalent silver oxide which is unstable and easily dissolves in aqueous alkaline solution accelerates the leakage of the alkaline electrolyte to the outside since the internal pressure of the cell is raised by the O.sub.2 gas gradually accumulated therein.
To eliminate the above--noted drawbacks a method of coating the surface of the AgO powder with plumbic acid silver is disclosed in U.S. Pat. No. 3,017,448. Since the surface of the AgO powder coated with the plumbic acid silver is hard to be reduced, the silver layer is hard to be formed on the surface of the positive electrode pellet and thus the battery impedance becomes higher.
The O.sub.2 gassing volume in case Zn, Cd, Hg, Al, In, Tl, Sn, Pb or W are added to AgO powder by 1000 PPM has been investigated by Aldar Tvarusko in J. Electrochem. Soc:, 116, 1071 (1969). Further, the effect of Cd, Al, Pb, V and Cr presented in the above paper for improving the stability of AgO is not sufficient.